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Blog of Rick Boozer, astrophysicist
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Thursday, July 6, 2017

BE SAFE!!! Don’t Misuse Solar Eclipse Viewing Glasses

-- And Other Safe Ways to View a Solar
Eclipse --

Viewing a solar eclipse improperly can put your eyesight in
danger.With the upcoming eclipse on
August 21, now is a good time to discuss various methods to see the eclipse
safely.

By now, everyone has probably heard about the special
eclipse viewing glasses being made available.At the Anderson
Jockey Lot, 1000 pairs of these glasses will be given away on the day of
the eclipse (yes, at NO charge) as long as supplies last.Many organizations and companies are also offering
such glasses for free as a public service.These glasses are only needed during the period of the eclipse when part
of the Sun is not covered by the Moon’s disk.The only time you can safely look at the eclipse directly without
the special glasses is during the scant few minutes that the disk of the Sun is
fully hidden (at totality).Indeed,
during that brief totality you are encouraged to look directly at the eclipse
to get the full effect in all of its glory.The special glasses will be needed again as soon as totality is over,
should you continue watching the Sun.

However, it is necessary to use the glasses in the way the manufacturer
recommends to properly protect your precious eyesight!Even when looking through the special eclipse
glasses, you should observe the Sun for no longer than 3 minutes at a time
with at
least a 20-minute break in between each 3-minute observation.Indeed, you will not miss anything by not
looking at the Sun frequently before totality, because the Moon’s disk will
gradually cover the Sun’s disk at a very slow imperceptible rate.Those who wear prescription glasses should
place the eclipse glasses in front of their regular glasses, as I am pictured
doing in the above photo.

But there are safe ways to constantly view the eclipse, even before and after totality.Those of you who have read one
of my earlier articles know that you can see all the sunlit periods (called
partial phases) of the eclipse by
looking in the shade cast by a leafy tree.If there is not a tree around, you can use a common kitchen
colander.The holes in that utensil will
project nice multiple images of the eclipsing Sun onto any surface you choose if hold the
colander far enough away from the surface.

NEVER look at the Sun directly through binoculars or a
telescope at any time, whether there is an eclipse or not.However, if you own either of those, there is
a safe way to use them to observe the solar eclipse.If using binoculars, it is best to use an
adapter (available for a few dollars) to mount the binoculars to a camera
tripod.Again, DO NOT LOOK AT THE SUN
DIRECTLY THROUGH THE BINOCULARS.While
holding a white piece of cardboard behind the binoculars, tilt the binoculars with
the mount until you see the shadows of the binocular’s tubes as perfectly round
circles. At that time, the binoculars will be pointing directly at the
Sun.Now, move the cardboard far enough
away from the binoculars for the Sun’s image (projected onto the cardboard by
the binoculars) to appear at least 3 inches wide.Looking at the image of the Sun, focus the
binoculars until the disk of the Sun is sharp around the edges.Click here
to see a photo such a binocular projected image.

The same technique can be used with a small telescope, but the telescope should
have a main lens or mirror no wider than 3 inches (75 mm) to avoid overheating.

Another way to safely observe the eclipse with binoculars or
telescope is to buy professionally made full-aperture filters.This method may be the easiest and most
convenient way to use a telescope or binoculars to observe the Sun.Here are a couple of sources: Thousand
Oaks Optical and Orion
Telescopes.

I hope you have found this article useful.Have fun experiencing the once-in-a-lifetime
total solar eclipse, but most of all, stay safe.You are invited to join us at the Anderson
Jockey Lot where we will have the longest totality along the I-85 corridor
lasting 2 minutes and 40 seconds!

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I give public presentations on astronomy and space travel.

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